How much spending money for Lisbon and things to do?

Hello, Myself and my friend are going on a girls holiday to Lisbon, we will get to Lisbon at around 23:00 on Saturday 11th June and will leave at 21:00 on Wednesday 15th June, so will be in Lisbon for 4 nights and 4 full days, we are staying in an Air bnb apartment in the Madragoa neighborhood, which has a kitchen so we may have the odd meal there, however our days will mostly be spent eating and drinking (we drink quite a lot) sun bathing at near by beaches, seeing the sights and going out at night. Could anyone roughly advise how much spending money we would need for those 4 full days or how much a day would be advised? We would also appreciate any advice on things to do for two girls in their late 20's, places to eat, any good nightlife spots or day parties, good sun bathing spots and how to get to the best beaches from Lisbon and cost of trains there? Any help on this would be much appreciated. Many thanks, Abby